A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Presently in lithography, use may be made of a stationary magnet (i.e. moving coil) motor to drive a support, e.g. a substrate support or a patterning device support. When making use of a stationary magnet motor, a stationary magnetic field is generated. Due to the high demands on throughput and processing speed of the lithographic apparatus, a high power motor is required, which translates into a strong magnet hence resulting in a high magnetic field strength.
In a lithographic apparatus, a position of the support (e.g., substrate support) may be measured making use of an optical measurement device, such as an encoder and/or an interferometer. Making use of such an optical measurement device, a position of the support in question can be measured with respect to a reference, such as a metrology frame of the lithographic apparatus or a projection system thereof.